Rhubarb Meringue Pie

Ingredients

• 1 frozen pie crust
• 3 1/2 to 4 cups chopped rhubarb stalks
• 3/4 cup white granulated sugar
• 1 Tbsp orange zest
• 1/4 teaspoon cinnamon
• 1/4 teaspoon ground ginger
• 3 Tbsp instant tapioca or 2 Tbsp tapioca flour/starch
• 1 Tbsp cornstarch
• 1/3 cup cold water
• 1/4 teaspoon cream of tartar
• 1/2 cup white granulated sugar
• 4 large egg whites, room temperature
• 1/2 teaspoon vanilla extract

Directions

1. Bring your oven to 350 degrees F. Cover the frozen pie shell with aluminum foil, then add pie weights until the shell is roughly two-thirds full; dried beans are perfectly fine here. Bake for 20 minutes, take the crust out, and use the foil edges to lift away the weights and foil. Prick the base of the crust all over with a fork.
2. Slide the crust back into the oven and continue baking for 10 to 15 minutes, until the whole shell has taken on a pale golden color. Take it out and leave it nearby.
3. For the filling, combine the chopped rhubarb, sugar, orange zest, cinnamon, and ground ginger in a medium saucepan, stirring carefully so the fruit stays in decent pieces. Let it stand for 15 minutes, which gives the sugar time to pull out the rhubarb juices. Set the saucepan over medium heat and stir in the instant tapioca or tapioca starch. If instant tapioca bits bother you, buzz them in a blender first so they turn into a finer flour. Warm the rhubarb slowly until it gives off steam. Don’t hurry this part, since high heat can turn the fruit into a soft rosy slump; you want the pieces just tender, not collapsed.
4. Set the oven to 325 degrees F.
5. While the rhubarb cooks, begin the meringue. Whisk the sugar with the cream of tartar in a small bowl and keep it ready. The cream of tartar helps the meringue hold its shape, but if you do not have it, you can use a teaspoon of white vinegar instead, adding it to the egg whites when whipping begins. In a small saucepan, whisk the cornstarch into the cold water until no dry spots remain. Put the pan on the stove and keep whisking until the mixture bubbles and turns into a gel, then take it off the heat.
6. Check that the egg whites have no yolk or shell in them, and that the bowl for your mixer is completely clean. Even a little leftover fat in the bowl can keep the whites from whipping properly. Add the egg whites and vanilla to the bowl of an electric mixer. Begin on low speed, then ease the mixer up to medium. When the whites look foamy, add the sugar and cream of tartar mixture gradually, one tablespoon at a time. Beat until the sugar has mixed in and the meringue makes soft peaks. Add the cornstarch gel the same way, one tablespoon at a time. Turn the mixer to high and beat until stiff peaks form, stopping before you take it too far.
7. The rhubarb filling should be very hot when the meringue is added, so warm it back up until steamy if it has cooled down. Pour the rhubarb into the prebaked crust and spread it evenly across the bottom.
8. Right away, spoon the meringue over the filling, using a rubber spatula to cover the outer edge first and then the middle so it does not sink. Press the meringue so it meets the crust all the way around, which helps keep it from pulling back. Use the back of a spoon to make peaks across the top.
9. Bake the pie at 325 degrees F until the meringue turns golden, about 20 minutes. Move it to a wire rack and let it cool to room temperature. You can refrigerate the pie, though it is at its best the day it is made.